Recent researches have been revealing that some complex lipids, particularly some glycolipids exhibit pronounced physiological activities. For example, it has come to be known that ceramides composed of sphingosine and fatty acids and cerebrosides composed of sphingosine, sugar, and fatty acids are present in the stratum corneum of human skin and serve to prevent evaporation loss of water from the body. Application of the glycolipids to the cosmetics taking advantage of this high moisturizing activity and application to pharmaceuticals taking advantage of elastase inhibitory activity or free radical inhibitory activity have advanced.
Ceramide related substances typified by the sphingoglycolipids have been supplied as extract from bovine brain, etc. However, since the BSE (bovine spongiform encephalopathy) outbreak in 1986 the supply has decreased markedly because of the risk of human infection. The demand for safe ceramide related substances of plant origin has thus been increasing.
Seeing that ceramide related substances of plant origin are by no means inferior to those of animal origin and involve neither side effects nor toxicity as has recently been revealed, extraction of ceramide related substances from plant raw materials are now under intensive study. Sphingoglycolipids of plant origin, particularly glycosylceramides, that have hitherto been reported include those obtained from cereals and beans, such as rice (see Agric. Biol. Chem., vol. 49, p. 2753 (1985)), rice bran (see JP-A-62-187404 and JP-A-11-279586), wheat (see Agric. Biol. Chem., vol. 49, 1. 3609 (1985) and a published Japanese translation of a PCT patent application No. Hei.-6-507653), and soybeans (see Chem. Pharm. Bull., vol. 38, No. 11, p. 2933 (1990)).
Ceramides have been added to skin care products, hair care products, bathing preparations, and the like so that the manner of taking in ceramides has been almost restricted to percutaneous absorption. In recent years, it has been reported that one-month administration of 20 mg/day of wheat extract containing 3 wt % of wheat ceramides results in improvement on skin's moisture retention (see Fragrance Journal, vol. 23, No. 1, p. 81 (1995)), and oral intake of ceramides in the form of eatable cosmetics has been attracting attention.
Cosmetics containing ceramides of animal (horse) origin, ceramides produced by yeast fermentation or synthetic ceramides are now commercially available. Being safe, ceramides of plant origin have a favorable image, and many cosmetics featuring the plant origin are on the market.
However, plants which have been so far utilized as materials for supplying plant sphingoglycolipids are limited to cereals and beans, of which the sphingoglycolipids content is not much, usually about 0.01% by weight. All of these plant materials are edible for human consumption, whereas residue after extracting sphingoglycolipids therefrom has no value as food. The problem of using plants lies in that a vast quantity of food materials lose their value as food only to provide a slight amount of sphingoglycolipids. Looking out over the food processing industry, on the other hand, it is noted that 3,000 to 4,000 tons of “tobiko” powder occurs a year as a by-product in making konjac products (devil's tongue) from konjac (elephant foot or Amorphophallus konjac). Tobiko powder finds no use as a food due to its peculiar acrid taste and irritating smell, except that part of tobiko powder is made use of as a fertilizer or a concrete thickener. Further, cotton seed oil cake, which is a by-product in squeezing cotton seed to obtain cotton seed oil, had been used as an animal feed rich in vegetable protein until 10 years ago. However, giving cow cotton seed as a high-energy feed is increasing among dairy farmers aiming to improve fat content in milk. Increase of utility of cotton seed oil cake is therefore demanded.
The present invention relates to functional foods and cosmetics containing sphingoglycolipids of plant origin which are attracting attention as a functional material of cosmetics and foods. It is an object of the present invention to provide functional foods and cosmetics made of materials of plant origin which are rid of the safety problem often pointed out in relation to the conventional materials extracted from animal tissue and yet find no value as food for the time being.